The present invention relates to the technological sector which manufactures polyurethane foams and more specifically to the mineral fillers used in this sector, in particular fillers of the carbonate, hydroxide, silicate and sulphate type and similar mineral fillers.
It is known that polyurethane foam (or PUR) is obtained by the reaction of a polyol on an isocyanate such as toluene diisocyanate or TDI, concurrently with a reaction of the isocyanate on water.
To produce block foam, the xe2x80x9cmixing headxe2x80x9d is charged either with a master batch of polyol and mineral additive on the one hand and on the other hand the remaining polyol, the catalyst system such as an amine catalyst, tin catalyst or any other catalyst, one or more surface active agents, generally of the silicon type, water, toluene diisocyanate, optionally an auxiliary foaming agent which may be methylene chloride, acetone and various additives such as heat stabilising agents or, alternatively, with the polyol in which the master batch has been diluted to the desired concentration beforehand and on the other the above-mentioned additives (catalyst, surface active agent, etc . . . ).
The reaction of the water on the isocyanate, catalysed by the amine, generates CO2 which forms the foam.
In order to reduce the cost price per litre and per kilogram of objects made from flexible, semi-rigid or rigid polyurethane foam, which may or may not be moulded, it has become increasingly necessary to increase the quantity of filler contained in the flexible, semi-rigid or rigid polyurethane foams whilst conserving or improving their physical-chemical properties, such as compression modulus or tear strength, or improve their aesthetic or other qualities such as their fireproof qualities, a required by the different fields of industry such as the automotive, furniture, building and other industries.
These days, there are several methods of incorporating the mineral fillers with these polyurethane compounds.
In a first type of method (FR 2 651 236), calcium carbonate is introduced into a polyurethane plasticiser. This method of producing a suspension of filler in a plasticiser, which allows the proportion of filler in the polyurethane compound to be increased, has proved to be expensive and too awkward to implement when manufacturing flexible, semi-rigid or rigid polyurethane foams because of the accompanying deterioration in the physical and chemical properties of the foams obtained using this filler suspension.
Attempts were then made to introduce the mineral fillers to the flexible, semi-rigid or rigid polyurethane foams in a simpler, less costly manner, eliminating the inherent problem which causes a significant reduction in the reaction capacity of the polyurethane foams.
To this end, various methods of introducing the filler into a polyol, one of the ingredients of polyurethane, have become known to those skilled in the art.
A first type of method is based on a teaching of grafting methacrylic acid (DE 2 654 746, DE 2 714 291, DE 2 739 620) or another vinyl compound such as styrene onto the polyol. However, with this type of method the calcium carbonate suspension in the polyol becomes unworkable, being too difficult to handle due to a very high viscosity and a poor distribution of the filler in the medium in conjunction with problems caused by sedimentation of the suspension.
Another type of method consists in treating the surface of the filler before it is introduced into the polyol using an agent, which might be an alcohol with 8 to 14 carbon atoms for example (FR 2 531 971) or a phosphate of hydroxycarboxylic acid (EP 0 202 394).
However, these methods produce the same type of disadvantages as those outlined above because the user is faced with problems caused by the poor capacity of the mineral filler treated in this way to disperse in the polyol.
Another method of treating a mineral filler has been developed (EP 0 726 298) using at least one agent of the organic phosphate type for treatment purposes, in conjunction with a treated mineral filler, producing a suspension of mineral filler in the polyols which has a high filler content and a low viscosity, i.e. a homogeneous suspension which is not susceptible to sedimentation or to decantation, nor does it inherently thicken when manufacturing flexible, semi-rigid or rigid polyurethane foam.
According to this document, the mineral fillers are treated with a view to placing them in suspension in the polyols with the aid of at least one agent of the organic phosphate type for treatment purposes, having the general formula (1): 
where R1=either H or alkyl with 8 to 40 carbon atoms or aryl or alkylaryl or arylalkyl with 6 to 40 carbon atoms
where R2=either alkyl with 8 to 40 carbon atoms or aryl or alkylaryl or arylalkyl with 6 to 40 carbon atoms
X=xe2x80x94CH2xe2x80x94CH2xe2x80x94
Y=CH(CH3)xe2x80x94CH2xe2x80x94 or xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94
(m+n) varies from 0 to 30 where mxe2x89xa630 and nxe2x89xa630
(p+q) varies from 0 to 30 where pxe2x89xa630 and qxe2x89xa630.
This latter technique is satisfactory but a new problem has been encountered in connection with a specific and more recent technique of manufacture of PUR foams.
According to the conventional method, the mixer head is charged with a mixture of polyol and mineral filler on the one hand and the remaining polyol, TDI, an auxiliary foaming agent such as methylene chloride and various additives such as a tin salt and a surfactant, generally of the silicon type, on the other. The reaction generates CO2 in situ, as mentioned above, which forms the foam. Formation of the foam passes through two main stages, the first occurring at the onset of foaming and the second when the foam block is being stabilised, after which a mass of PUR foam is produced which is then cut into blocks of the desired dimension in order to make mattresses, seat coverings, etc . . .
A new method has been developed in recent years and is described in particular in patents EP 0 645 226 and WO 96/00644, whereby the CO2 is injected into the mixing head directly or through the polyol flow in the liquid state. The CO2 is therefore used as an auxiliary blowing agent.
This method has advantages, particularly in terms of reducing in quite a remarkable way the use and formation of toxic or inflammable products and is likely to take on increasing importance in the future.
However, this new method does have technical problems in addition to those inherent in manufacturing PUR foam.
In order to implement a method of this type correctly, known as PUR foam with CO2 or xe2x80x9cCO2 methodxe2x80x9d, it seems to be necessary to reduce significantly the time needed to mix the filler with the polyol and to improve the mixing quality.
As proposed by this invention, it has been found that the problem of the mixing time and the difficulties inherent in the new CO2 method can be resolved by treating a mineral filler in a manner comparable to the techniques described in EP 0 726 298, but with significant improvements.
Surprisingly, it was also discovered whilst conducting research into the CO2 method that the method used to treat the mineral fillers as proposed by the invention also improves the conventional processes used to manufacture PUR foams.
Accordingly, the invention is not limited to the CO2 processes, which was the original problem to be resolved, but on the contrary is applicable in a general manner.
It has also been found that the method proposed by the invention for treating mineral fillers can be applied to the methods used to manufacture composite materials with a PUR matrix, whether or not they are cellular, and that whatever the filler used: CaCO3, talcs, kaolins, aluminium hydroxide, magnesium hydroxide, etc . . . in numerous applications in the field of accessories for the automotive industry, for the transport sector, in particular road or rail and for industrial objects used in a variety of applications.
By the terms xe2x80x9ccomposite materialsxe2x80x9d or xe2x80x9ccomposite PURxe2x80x9d used here is meant polyurethanes reinforced with vegetable fibres, glass or quartz or synthetic fibres, cut fibres in general, or similar. By the expression xe2x80x9ccellular PURxe2x80x9d used here is meant polyurethanes, whether they are expanded or not.
The invention relates to a method of treating mineral fillers of a specific grain size with the aid of processing agents of the organic phosphate type, incorporating a de-agglomeration stage and optionally a selection stage, with a view to improving the techniques applied to manufacturing PUR foams either by foaming without an auxiliary blowing agent or foaming with an auxiliary blowing agent such as methylene chloride, acetone or CO2 or others, and composite PURs, whilst reducing the time taken to mix the filler treated in this way, with the polyol and other reagents and overcoming the specific difficulties encountered with regard to the filler agglomerates which clog the static dispersing equipments provided for the CO2 and which tend to detract from the mechanical properties of PUR foams and composites, cellular or not, such as the tear strength of PUR foams, for example.
More specifically, the invention relates to a method of treating mineral fillers, characterised in that the filler:
a) is treated using at least one compound of the general formula (1): 
xe2x80x83where R1=either H or alkyl with 8 to 40 carbon atoms or aryl or alkylaryl or arylalkyl with 6 to 40 carbon atoms
where R2=either alkyl with 8 to 40 carbon atoms or aryl or alkylaryl or arylalkyl with 6 to 40 carbon atoms
X=xe2x80x94CH2xe2x80x94CH2xe2x80x94 or xe2x80x94CH(CH3)xe2x80x94CH2xe2x80x94or xe2x80x94CH2xe2x80x94CH(CH3) or xe2x80x94(CH2)5xe2x80x94COxe2x80x94
Y=xe2x80x94CH2xe2x80x94CH2xe2x80x94 or xe2x80x94CH(CH3)xe2x80x94CH2xe2x80x94or xe2x80x94CH2xe2x80x94CH(CH3)xe2x80x94 or xe2x80x94(CH2)5xe2x80x94COxe2x80x94
X and Y being the same or different,
(m+n) varies from 0 to 60 (boundaries included) as well as (p+q) where 0xe2x89xa6m+nxe2x89xa660 and 0xe2x89xa6p+qxe2x89xa660 when X=Y=xe2x80x94CH2xe2x80x94CH2xe2x80x94and
where (1xe2x89xa6mxe2x89xa610 and 1xe2x89xa6pxe2x89xa610) and (0xe2x89xa6nxe2x89xa659 and 0xe2x89xa6qxe2x89xa659) if X is different from Y.
b) undergoes a de-agglomeration step and
c) optionally undergoes a selection step.
Said filler is of a specific grain size as described below.
By the term xe2x80x9cde-agglomerationxe2x80x9d is meant a step whereby the number of agglomerates are reduced using an appropriate apparatus, of the crusher type, more specifically a crusher of the pin type or known xe2x80x9cattritorxe2x80x9d type. The agglomerates can be evaluated by a known method in accordance with the North gauge procedure, which is governed by a standard (ISO 1524).
By xe2x80x9cselectionxe2x80x9d is meant the operation whereby a certain range within the grain size is separated by passage through xe2x80x9cseparatorsxe2x80x9d (screens, dynamic classifiers, etc . . . which are known). An operation of this type does not affect the quality of the product but the skilled person will be able to decide whether to apply it or not as a means of optimising the product, depending on the anticipated end use.
By xe2x80x9cspecific grain sizexe2x80x9d for the purposes of the invention is meant that the grain size must be neither too fine nor too coarse and should be produced directly by crushing or by mixing fillers. In one illustrative but not restrictive example, given in order to provide an understanding of this criterion, the filler may substantially have a mean diameter of d50 in terms of grain size. This mean diameter for the mineral fillers proposed by the invention will be between 0.1 micrometres and 15 micrometres, preferably between 0.1 micrometres and 10 micrometres and most preferably between 0.3 and 8 micrometres. Furthermore, the person skilled in the art will know how to make up fillers which comply with this requirement.
The invention also relates to mineral fillers of a specific grain size treated with this treatment agent by a de-agglomeration step, and optionally a selection step, requiring a shorter time to mix the filler thus treated with the polyol and other reagents and intended to be placed in suspension in a polyol with a view to use in the manufacture of polyurethane foams either by foaming without an auxiliary blowing agent or foaming with an auxiliary blowing agent such as methylene chloride, acetone or CO2 or others, or composite PURs, and more specifically mineral fillers of the carbonate type treated by this method and for this purpose.
The invention also relates to suspensions in the polyols of the mineral fillers so treated, prepared so that they can be incorporated in a method of manufacturing PUR foams either by foaming without an auxiliary blowing agent or foaming with an auxiliary blowing agent such as methylene chloride, acetone or CO2 or others, as well as their use in the manufacture of flexible, semi-rigid or rigid polyurethane foams by the method either by foaming without an auxiliary blowing agent or foaming with an auxiliary blowing agent such as methylene chloride, acetone or CO2 or others and for the manufacture of composite polyurethanes.
In addition, the invention relates to the actual foams obtained by a method involving either by foaming without an auxiliary blowing agent or foaming with an auxiliary blowing agent such as methylene chloride, acetone or CO2 or others, or composite polyurethanes, cellular or not, containing the fillers treated by the method of the invention in a mixture with polyol.
Furthermore, the invention relates to the use of flexible, semi-rigid or rigid polyurethane foams or composites, cellular or not, thus obtained for the manufacture of moulded or non-moulded objects.
The invention also relates to the preliminary mixtures with a polyol of the fillers treated by the method of the invention and in particular in proportions appropriate to the manufacture of polyurethanes and more specifically polyurethane foams or composite PURs.
In a preferred embodiment of the invention, the filler will be used immediately it leaves the manufacturing equipment, the moisture content of which will be compatible with its application.
Most preferably, the mineral filler will be treated with an acid phosphate of aliphatic alcohol, branched or not, with 8 to 20 carbon atoms, onto which 0 to 12 ethylene oxide chains are condensed, and may optionally contain a mixture of mono-esters and di-esters.
The treatment proposed by the invention is implemented dry or wet.
The mineral fillers treated as proposed by the invention and which enable stable and homogeneous suspensions to be obtained in the polyols are selected from among the mineral fillers which impart to polyurethane foams and PURs used to make up composites with a PUR matrix, cellular or not, physical and chemical properties that are compatible with the use to which these products will be put when manufacturing objects, moulded or not, and are selected in particular from among the carbonates, phosphates and sulphates of natural or synthetic alkaline earths such as, in particular, calcium carbonates of natural or synthetic origin, magnesium carbonate, zinc carbonate, the combined salts of magnesium and calcium such as dolomites, lime, magnesia, barium sulphate, calcium sulphates, magnesium hydroxides, aluminium hydroxides, silica, wollastonite, the clays and other silico-alumina such as the kaolins, silica-magnesia such as talc, mica, solid or hollow glass beads, the metal oxides such as zinc oxide, the iron oxides, titanium oxide and more specifically selected from among the natural or precipitated calcium carbonates such as chalk, calcite, marble, the dolomites, aluminum hydroxide, magnesium hydroxide, talc or mixtures thereof.
The mineral fillers proposed by the invention are distinctive compared with those of the prior art due to the fact that they retain their hydrophilic properties and exhibit an up-take of polyol which is reduced by at least 15% and preferably at least 20% as compared with an untreated mineral filler and more specifically the fact that they are obtained by the method of the invention.
By xe2x80x9cpreferablyxe2x80x9d is meant that the invention also covers the values of between 15% and 20% although the effectiveness of the results is better the greater the decrease in polyol take-up.
By definition, the polyol take-up, which represents the absorption capacity of the fillers, is the number of milligrams or grams of polyol used for 100 g or 100 ml of filler substance under the test measurement conditions stipulated by a method based on the ISO 787/5 standard.
The polyols used belong to the family of polyethers and polyesters-polyethers and the polyesters.
Amongst the common polyol polyethers, mention may be made, for example, of the addition products of propylene oxide on a simple polyol such as, for example, glycol, glycerol, trimethylolpropane, sorbitol, in the presence of ethylene oxide or not. However, mention may also be made of the special polyol polyethers such as, for example, the amine-based polyethers obtained by the addition of propylene oxide or optionally ethylene oxide on amines, halogen polyethers, grafted polyethers resulting from the copolymerisation of styrene and acrylonitrile in suspension in a polyether, or alternatively polytetramethylene glycol.
Amongst the polyol polyesters, mentioned may be made, for example, of those resulting from the polycondensation of polyalcohols on polyacids or their anhydrides, such as the diacids, such as, for example, adipic, phthalic or other diacids, reacting with diols (for example ethylene glycol, propylene glycol, butylene glycol or others), triols (for example glycerol, trimethylolpropane or others) and tetrols (for example pentaerythritol or others, alone or in a mixture).
Other polyols which may also be mentioned are various hydroxyl compounds such as, for example, hydroxylated polybutadienes, the prepolymers with hydroxyl terminations (resulting from the reaction of excess polyol on a diisocyanate) or the simple polyols such as, for example, glycerol, amino alcohols used in a small quantity with the polyol polyethers or the polyol polyesters in order to increase cross-linking.
The suspensions of mineral fillers in the polyols, as proposed by the invention, which may also contain other mineral and/or organic products such as catalysts and/or anti-oxidants and/or others, are characterised in that the concentration of dry substance of the treated mineral substances may be as high as 80% by weight, and in that they are not susceptible either to decantation or sedimentation or damning thickening after storage for 7 days in readiness for the manufacture of flexible, semi-rigid or rigid polyurethane foams, i.e. having a stable apparent Brookfield viscosity which is lower than that of suspensions of mineral fillers which have not been treated and in that they contain 0.5% to 3% by weight, relative to the weight of the mineral filler, of at least one treatment agent having the general formula (1).
An additional objective of the invention is to produce homogenous, stable and low-viscosity suspensions of these treated mineral fillers in the polyols, characterised by a concentration by weight of mineral fillers which may be as high as 80% and a content of treatment agent which may range from 0.5% to 3% by weight relative to the dry weight of the filler and containing no agglomerates.
These homogeneous, stable, low-viscosity suspensions proposed by the invention are easy to handle because they do not exhibit, under the normal conditions in which they are used by the skilled person, any occurrence of decantation, i.e. the separation in two phases, of sedimentation, i.e. the presence of a hard deposit at the bottom of the tank in which the suspension is stored, nor is there any damning thickening, which means that it will be possible to produce flexible, semi-rigid or rigid polyurethane foams or composite PURs, cellular or not, with excellent physical and chemical properties.
Finally, another objective of the invention is the use of these homogeneous, stable and low-viscosity dispersions of mineral fillers for the manufacture of flexible, semi-rigid or rigid polyurethane foams or cellular or non-cellular composites as well as the use of these foams or these composites for the manufacture of objects which may or may not be moulded.
The homogeneous, stable and low-viscosity suspensions filled in this manner, as proposed by the invention, exhibit a specific feature in that they can be used for the manufacture of polyurethane foams, regardless of whether they are flexible, semi-rigid or rigid, or for the manufacture of polyurethane composites, which may be cellular or not.
Furthermore, the flexible, semi-rigid or rigid polyurethane foams, cellular or not, obtained by using the suspensions of mineral fillers, treated as proposed by the invention, in polyols are used to make objects which may or may not be moulded.
Other features and advantages of the invention will become clear from the description given below.
The scope and interest of the invention will be more readily appreciated from the examples given below, although these are not intended to be restrictive in any respect.